目录
实现效果
今天介绍一个有趣的gis小功能：动态轨迹播放！效果就像这样：
这效果看着还很丝滑！别急，接下来教你怎么实现。代码示例基于parcel打包工具和es6语法，本文假设你已经掌握相关知识和技巧。
gis初学者可能对openlayers（后面简称ol）不熟悉，这里暂时不介绍ol了，直接上代码，先体验下感觉。
创建一个地图容器
引入地图相关对象
import Map from 'ol/Map';import View from 'ol/View';import XYZ from 'ol/source/XYZ';import {Tile as TileLayer, Vector as VectorLayer} from 'ol/layer';创建地图对象
const center = [-5639523.95, -3501274.52];const map = new Map({ target: document.getElementById('map'), view: new View({ center: center, zoom: 10, minZoom: 2, maxZoom: 19, }), layers: [ new TileLayer({ source: new XYZ({ attributions: attributions, url: 'https://api.maptiler.com/maps/hybrid/{z}/{x}/{y}.jpg?key=' + key, tileSize: 512, }), }), ],});创建一条线路
画一条线路
可以用这个geojson网站随意画一条线，然后把数据内容复制下来，保存为json文件格式，作为图层数据添加到地图容器中。
你可以用异步加载的方式，也可以用require方式，这里都介绍下吧：
// fetchfetch('data/route.json').then(function (response) { response.json().then(function (result) { const polyline = result.routes[0].geometry; }),};// requirevar roadData = require('data/route.json')后面基本一样了，就以fetch为准，现在把线路加载的剩余部分补充完整：
fetch('data/route.json').then(function (response) { response.json().then(function (result) { const polyline = result.routes[0].geometry;// 线路数据坐标系转换 const route = new Polyline({ factor: 1e6, }).readGeometry(polyline, { dataProjection: 'EPSG:4326', featureProjection: 'EPSG:3857', });// 线路图层要素 const routeFeature = new Feature({ type: 'route', geometry: route, }); // 起点要素 const startMarker = new Feature({ type: 'icon', geometry: new Point(route.getFirstCoordinate()), }); // 终点要素 const endMarker = new Feature({ type: 'icon', geometry: new Point(route.getLastCoordinate()), }); // 取起点值 const position = startMarker.getGeometry().clone(); // 游标要素 const geoMarker = new Feature({ type: 'geoMarker', geometry: position, });// 样式组合 const styles = { // 路线 'route': new Style({ stroke: new Stroke({ width: 6, color: [237, 212, 0, 0.8], }), }), 'icon': new Style({ image: new Icon({ anchor: [0.5, 1], src: 'data/icon.png', }), }), 'geoMarker': new Style({ image: new CircleStyle({ radius: 7, fill: new Fill({color: 'black'}), stroke: new Stroke({ color: 'white', width: 2, }), }), }), };// 创建图层并添加以上要素集合 const vectorLayer = new VectorLayer({ source: new VectorSource({ features: [routeFeature, geoMarker, startMarker, endMarker], }), style: function (feature) { return styles[feature.get('type')]; }, });// 在地图容器中添加图层 map.addLayer(vectorLayer);以上代码很完整，我加了注释，整体思路总结如下：
- 先加载路线数据
- 构造路线、起始点及游标对应图层要素对象
- 构造图层并把要素添加进去
- 在地图容器中添加图层
添加起、终点
这个上面的代码已经包括了，我这里列出来是为了让你更清晰，就是startMarker和endMarker对应的代码。
添加小车
同样的，这里的代码在上面也写过了，就是geoMarker所对应的代码。
准备开车
线路有了，车也有了，现在就到了激动人心的开车时刻了，接下来才是本文最核心的代码！
const speedInput = document.getElementById('speed'); const startButton = document.getElementById('start-animation'); let animating = false; let distance = 0; let lastTime; function moveFeature(event) { const speed = Number(speedInput.value); // 获取当前渲染帧状态时刻 const time = event.frameState.time; // 渲染时刻减去开始播放轨迹的时间 const elapsedTime = time - lastTime; // 求得距离比 distance = (distance + (speed * elapsedTime) / 1e6) % 2; // 刷新上一时刻 lastTime = time; // 反减可实现反向运动，获取坐标点 const currentCoordinate = route.getCoordinateAt( distance > 1 ? 2 - distance : distance ); position.setCoordinates(currentCoordinate); // 获取渲染图层的画布 const vectorContext = getVectorContext(event); vectorContext.setStyle(styles.geoMarker); vectorContext.drawGeometry(position); map.render(); } function startAnimation() { animating = true; lastTime = Date.now(); startButton.textContent = 'Stop Animation'; vectorLayer.on('postrender', moveFeature); // 隐藏小车前一刻位置同时触发事件 geoMarker.setGeometry(null); } function stopAnimation() { animating = false; startButton.textContent = '开车了'; // 将小车固定在当前位置 geoMarker.setGeometry(position); vectorLayer.un('postrender', moveFeature); } startButton.addEventListener('click', function () { if (animating) { stopAnimation(); } else { startAnimation(); } });简单说下它的原理就是利用postrender事件触发一个函数，这个事件本来是地图渲染结束事件，但是它的回调函数中，小车的坐标位置一直在变，那就会不停地触发地图渲染，当然最终也会触发postrender。这样就实现的小车沿着轨迹的动画效果了。这段代码有点难理解，最好自己尝试体验下，比较难理解部分我都加上了注释。
好了，ol动态巡查已经介绍完了，动手试下吧！看你的车能否开起来？
完整代码
index.html
Marker Animation .map { width: 100%; height:400px; }
main.js
import 'ol/ol.css';import Feature from 'ol/Feature';import Map from 'ol/Map';import Point from 'ol/geom/Point';import Polyline from 'ol/format/Polyline';import VectorSource from 'ol/source/Vector';import View from 'ol/View';import XYZ from 'ol/source/XYZ';import { Circle as CircleStyle, Fill, Icon, Stroke, Style,} from 'ol/style';import {Tile as TileLayer, Vector as VectorLayer} from 'ol/layer';import {getVectorContext} from 'ol/render';const key = 'Get your own API key at https://www.maptiler.com/cloud/';const attributions = '© MapTiler ' + '© OpenStreetMap contributors';const center = [-5639523.95, -3501274.52];const map = new Map({ target: document.getElementById('map'), view: new View({ center: center, zoom: 10, minZoom: 2, maxZoom: 19, }), layers: [ new TileLayer({ source: new XYZ({ attributions: attributions, url: 'https://api.maptiler.com/maps/hybrid/{z}/{x}/{y}.jpg?key=' + key, tileSize: 512, }), }), ],});// The polyline string is read from a JSON similiar to those returned// by directions APIs such as Openrouteservice and Mapbox.fetch('data/polyline/route.json').then(function (response) { response.json().then(function (result) { const polyline = result.routes[0].geometry; const route = new Polyline({ factor: 1e6, }).readGeometry(polyline, { dataProjection: 'EPSG:4326', featureProjection: 'EPSG:3857', }); const routeFeature = new Feature({ type: 'route', geometry: route, }); const startMarker = new Feature({ type: 'icon', geometry: new Point(route.getFirstCoordinate()), }); const endMarker = new Feature({ type: 'icon', geometry: new Point(route.getLastCoordinate()), }); const position = startMarker.getGeometry().clone(); const geoMarker = new Feature({ type: 'geoMarker', geometry: position, }); const styles = { 'route': new Style({ stroke: new Stroke({ width: 6, color: [237, 212, 0, 0.8], }), }), 'icon': new Style({ image: new Icon({ anchor: [0.5, 1], src: 'data/icon.png', }), }), 'geoMarker': new Style({ image: new CircleStyle({ radius: 7, fill: new Fill({color: 'black'}), stroke: new Stroke({ color: 'white', width: 2, }), }), }), }; const vectorLayer = new VectorLayer({ source: new VectorSource({ features: [routeFeature, geoMarker, startMarker, endMarker], }), style: function (feature) { return styles[feature.get('type')]; }, }); map.addLayer(vectorLayer); const speedInput = document.getElementById('speed'); const startButton = document.getElementById('start-animation'); let animating = false; let distance = 0; let lastTime; function moveFeature(event) { const speed = Number(speedInput.value); const time = event.frameState.time; const elapsedTime = time - lastTime; distance = (distance + (speed * elapsedTime) / 1e6) % 2; lastTime = time; const currentCoordinate = route.getCoordinateAt( distance > 1 ? 2 - distance : distance ); position.setCoordinates(currentCoordinate); const vectorContext = getVectorContext(event); vectorContext.setStyle(styles.geoMarker); vectorContext.drawGeometry(position); // tell OpenLayers to continue the postrender animation map.render(); } function startAnimation() { animating = true; lastTime = Date.now(); startButton.textContent = 'Stop Animation'; vectorLayer.on('postrender', moveFeature); geoMarker.setGeometry(null); } function stopAnimation() { animating = false; startButton.textContent = '开车了'; geoMarker.setGeometry(position); vectorLayer.un('postrender', moveFeature); } startButton.addEventListener('click', function () { if (animating) { stopAnimation(); } else { startAnimation(); } }); });});package.json
{ "name": "feature-move-animation", "dependencies": { "ol": "6.9.0" }, "devDependencies": { "parcel": "^2.0.0-beta.1" }, "scripts": { "start": "parcel index.html", "build": "parcel build --public-url . index.html" }}参考资源：
https://openlayers.org/en/latest/examples/feature-move-animation.html
以上就是vue利用openlayers实现动态轨迹的详细内容，更多关于vue openlayers动态轨迹的资料请关注脚本之家其它相关文章！